1. Field of the Invention
The present invention relates to an alignment apparatus for aligning a semiconductor wafer in a predetermined position.
2. Description of the Related Art
A substrate inspection apparatus inspects the surface of a semiconductor wafer and detects a defect on the surface of the semiconductor wafer if any. The defect on the surface of the semiconductor wafer is, for example, a flaw, a chip, surface unevenness, dirt, and dust.
The substrate inspection apparatus comprises a wafer carrier for storing a plurality of semiconductor wafers, an inspection unit for performing a macro-inspection to visually inspect a semiconductor wafer and a micro-inspection to enlarge the surface of a semiconductor wafer using a microscope and inspect it, and a loader unit for removing a semiconductor wafer from the wafer carrier, passing the semiconductor wafer to the inspection unit, receiving the semiconductor wafer whose inspection has been completed in the inspection unit, and returning the wafer to the wafer carrier.
The inspection unit includes a wafer carrying apparatus for circularly carrying the semiconductor wafer received from the loader unit to a position of the macro-inspection and then that of the micro-inspection.
In the macro-inspection, a semiconductor wafer is rotated and rocked by a rocking mechanism to irradiate the surface of the semiconductor wafer with illumination for the macro-inspection. An inspector visually observes light reflected and scattered from the semiconductor wafer and detects a defect thereon.
In the micro-inspection, the defect on the surface of the semiconductor wafer, which has been detected by the macro-inspection, is enlarged using a microscope. An image of the enlarged defect is picked up by, for example, an image pickup device and displayed on a monitor. Thus, the inspector observes the type and size of the defect.
In the macro-inspection, however, the inspector visually observes a semiconductor wafer that is being rotated and rocked; therefore, it is difficult for the inspector to detect a defect if the semiconductor wafer is decentered and rotated.
It is thus necessary to lessen a decentering operation of the semiconductor wafer when the wafer is rotated and rocked.
For this reason, the semiconductor wafer is usually centered and passed to the inspection unit.
The centering method is executed as follows:
A case where an orthogonal robot is used in the loader unit will be described. The orthogonal robot includes an arm moving in the x-axis direction and an arm moving in the y-axis direction that intersects the x-axis direction at right angles.
The orthogonal robot removes a semiconductor wafer from the wafer carrier and passes it to the inspection unit. To perform the centering, when the semiconductor wafer crosses a plurality of sensors arranged on a wafer carrying path (before the wafer carrier), the sensors detect four points of the edge of the semiconductor wafer and obtains an amount of displacement of the semiconductor wafer from the center based on edge information of three of the four points.
When the semiconductor wafer is passed to the inspection unit, the amount of displacement of the semiconductor wafer from the center is corrected and the center of the wafer is aligned.
If an orthogonal robot is used in the loader unit that carries a semiconductor wafer from the wafer carrier to the inspection unit, a large space for moving the X and Y arms is required.
An articulated wafer-carrying robot is used in the inspection apparatus set up in a clean room since it is demanded that the carrying speed of semiconductor wafers and the setup space of the loader unit should be decreased.
The articulated wafer-carrying robot performs an operation for rotating an articulated arm, an operation for expanding and contracting the articulated arm to advance and retreat a hand, and an operation for lifting and lowering the articulated arm.
In the articulated wafer-carrying robot, however, a plurality of articulated arms are expanded, contracted and rotated, which complicates the control of an operation for aligning a semiconductor wafer. Furthermore, the distance from the position where an amount of displacement of the wafer from the center is obtained before the wafer carrier to the position of a delivery station of the inspection unit is long, and the articulated arms are rotated in the direction of the wafer carrier and that of the delivery station. It is thus difficult to center the semiconductor wafer with high precision.
An object of the present invention is to provide an alignment apparatus capable of aligning a target object such as a semiconductor wafer in a predetermined position.
An alignment apparatus according to the present invention, which aligns a target object in a predetermined position, comprises a carrying robot which carries the target object stored in a storage case to a delivery position of an installed apparatus, at least two optical sensors provided in the delivery position, which detects an outer circumference of the target object, moving means for moving the optical sensors and the target object relatively to each other to cause the outer circumference of the target object to fall within a field of view of the optical sensors, and alignment control unit which controls the carrying robot based on information of at least three points of the outer circumference detected by the optical sensors to align the target object in the predetermined position.
In an alignment apparatus according to another aspect of the present invention, the optical sensors are fixedly arranged at four points of the outer circumference of a largest-diameter one of a plurality of target objects with regard to a normal center of the delivery position, and the moving means positions an edge of the target object in each of the optical sensors.
In an alignment apparatus according to another aspect of the present invention, the optical sensors are fixedly arranged at four points on concentric circles corresponding to the outer circumferences of a plurality of target objects having different outside diameters with regard to a normal center of the delivery position.
In an alignment apparatus according to another aspect of the present invention, the moving mechanism moves the at least two optical sensors to respective points corresponding to outer circumferences of a plurality of target objects having different outside diameters.
In an alignment apparatus according to another aspect of the present invention, the optical sensors are arranged at four points on concentric circles with regard to a normal center of the delivery position, and the moving means moves the four optical sensors to positions on concentric circles corresponding to edges of a plurality of target objects having different outside diameters.
In an alignment apparatus according to another aspect of the present invention, the optical sensors are arranged in a position where concentric circles corresponding to the outer circumference of the target object having a largest outside diameter with regard to a normal center of the delivery position intersect the outer circumference of the target object having a small outside diameter.
In an alignment apparatus according to another aspect of the present invention, the moving mechanism is an articulated carrying robot comprising a rotating shaft that is rotatable in an axial direction, a plurality of joint arms coupled to each other to form an articulated arm, one end of the joint arms being provided on the rotating shaft, and a hand which is coupled to another end of the joint arms and holds the target object.
In an alignment apparatus according to another aspect of the present invention, the optical sensors comprise a two-dimensional image pickup device including an incident-light telecentric illumination system and obtains positional information of the outer circumference of the target object detected by the optical sensors from image data on one line or plural lines in a direction perpendicular to the outer circumference based on a two-dimensional image of the outer circumference of the target object.
In the alignment apparatus of the present invention configured as described above, when a target object stored in the storage case is carried to the delivery position of the installed apparatus by the carrying robot, at least two optical sensors are provided at the delivery position, these optical sensors are moved relatively to the target object, the outer circumference of the target is caused to fall within a field of view of each of the optical sensors, and the carrying robot is controlled based on information of at least three points of the outer circumference detected by the optical sensors, thereby aligning the target object in a predetermined position.